1. Field of the Invention
This invention relates to the field of disk drives, in particular to disk drive suspensions.
2. Description of Related Art
A disk drive generally uses one or more spinning storage disks, sometimes called storage media, to store data. Disks can be rigid, as used in hard drives, or flexible, as used in floppy drives. Disks commonly store data using magnetic methods or optical methods, and can spin at rates exceeding 15,000 revolutions per minute (rpm). Hard disk drives generally employ several rigid disks stacked one on top of another with spaces in between, attached to a common spindle. Floppy disk drives generally employ a single flexible disk in a bonded sleeve.
A disk, whether magnetic or optical, normally stores data in tracks which run in a spiral fashion around the disk. Because tracks are narrow and closely spaced in proportion to the diameter of a disk, the tracks approximately run tangentially around the disk. The term “tangentially” refers to directions which are in a plane parallel to the disk and at right angles to the disk's radial directions.
Over the surface of each disk in a disk drive, commonly on both sides of each disk, a read-write head is suspended in close proximity to the disk surface by a disk drive suspension. A disk drive suspension is sometimes referred to as a disk drive head suspension or simply a suspension. In hard disk drives with multiple disks on a spindle, suspensions operate in the spaces between the disks and on the two outer disk surfaces. A suspension is a cantilever beam-like feature, mounted on a movable actuator arm. The suspension extends to a precise but variable location above a disk. A suspension typically includes a mounting region, a hinge, load beam, gimbal, and flexure.
The combination of a suspension as discussed above, a read-write head, and a base plate which mounts the suspension to an actuator arm is sometimes called a suspension assembly or a head suspension assembly (HSA). A base plate is sometimes called a mount plate, mounting plate, or clad arm.
The load beam is a major arm-like part of the suspension which forms part of its structural backbone. An actuator arm supports the load beam at the load beam's proximal end, and the load beam supports the flexure at the load beams' distal end. The term “load beam” refers to a structure which may be unitary or may be composed of separately formed parts which are later affixed to one another.
The gimbal is held by the load beam over the disk. The gimbal retains the read-write head in a precise position near the load beam distal end while allowing the read-write head to pitch and roll slightly. A gimbal can be an integrally formed portion of a load beam, or it can be a separately formed part.
The flexure is typically referred to as a wiring layer or a circuit or one of several branded terms, i.e. Integrated Lead Suspension (ILS), Flex On Suspension (FOS), Integrated Lead Flexure (ILF), Electrical Lead Suspension (ELS), or Additive Circuit Gimbal (AGG). The flexure electrically connects the read-write head, located at the distal end of the suspension, to disk drive circuits at the proximal end of the head suspension. An electrical interconnect, sometimes referred to as “electrical leads,” is supported by the flexure and is often integrally formed with the flexure. The electrical interconnect carries electrical signals from the read-write head that are read from the disk across the suspension to disk drive circuitry. The flexure also carries electrical signals to be written to the disk from the disk drive circuitry across the suspension to the read-write head. The flexure can be integrally formed on a load beam.
The read-write head, also referred to as a head or a “slider,” contains the read-write transducer circuitry upon its proximal end. The slider surface facing the disk is designed and reactive-ion etched to define an aerodynamic pattern typically comprising rails that, in conjunction with the spinning disk, generate a positive pressure thereby lifting the slider from the spinning disk surface. The wind of the rapidly spinning disk running past aerodynamic pattern of protrusions on the slider creates the air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. The resultant boundary layer of air is commonly called an air bearing. The gram force of the load beam hinge pushes the slider toward the disk while the air bearing of the disk pushes away until an equilibrium position is reached. The equilibrium position is designed to be close enough to the disk so that the slider's read-write circuitry can interact with the disk but far enough away to prevent mechanical contact.
The suspension positions a read-write head over the middle of a single track during a single read or write operation. If the read-write head deviates left or right of a track then data may not be read or written correctly. This problem is sometimes called track misregistration (TMR). Therefore, it is important for the suspension to keep the slider positioned centrally over a track, and a laterally stiff suspension is thus preferred.
It is also preferable for a suspension's gimbal to pitch and roll freely, especially for smaller dimensioned sliders. Free pitch and roll movement requires low pitch and roll stiffness of the gimbal itself as well as the electrical interconnect which connects to the slider on the gimbal.
An “outrigger” is a longitudinal section of a suspension which is substantially separate from and extends beyond the side of the body of the suspension. An outrigger can include, among other things, an elongate gimbal spring arm, a flexure arm, or a section of electrical interconnect. Commonly, an outrigger refers to sections which are lateral to the gimbal or flexure tongue. An elongate gimbal spring arm is sometimes referred to as a stainless steel (SST) outrigger. A section of flexure or electrical interconnect configured as an outrigger is sometimes referred to as an “outrigger lead.” There can exist multiple outriggers on one side of a suspension which are displaced laterally one outside the other. An outrigger which is inboard of a second outrigger is sometimes referred to as an “inrigger.”
In the prior art, design techniques to reduce pitch and roll stiffness included reducing outrigger width or increasing outrigger length. However, these traditional methods are geometry-limited.